The present invention relates generally to printer consumables, and more specifically to memory components on printer consumables, and methods of utilizing information stored therein.
Printers with user-replaceable consumables (and related devices, such as facsimile machines and copiers) are well known in the art. For example, inkjet printers typically utilize replaceable ink supplies, either integrated with a printhead or in the form of separate supplies. When separate ink supplies are used in an inkjet printer system, typically the printheads are also separately replaceable and may also be considered a xe2x80x9cconsumable.xe2x80x9d In laser printers, toner is typically supplied in a replaceable cartridge, which may include the photosensitive drum on which images are formed.
Typically, printer systems include sensors to monitor conditions in the printer. For example, in inkjet printers, sensors may be used to detect characteristics of the ink and conditions such as a low or empty ink supply. The sensors are typically connected to an electronic controller in the printer, and allow the printer controller to modify the operation of the printer or to notify an operator of the printer status. The sensors may function by detecting a physical, optical, or chemical characteristic of the ink or toner, such as impedance or opacity. The printer controller or the driver software may adjust the operation of the printer based on comparing a measured sensor value to a reference threshold level that may be xe2x80x9chard codedxe2x80x9d into the printer controller firmware or the print driver software.
In situations where the printer controller must make a decision based on a comparison of a sensor measurement to a hard coded threshold value, several factors can lead to inaccurate results. First, the consumable material (such as ink) in different replaceable consumables may have different physical or chemical properties. The different properties may be the result of the different consumable materials being formulated for different applications, such as printing on different media. Sensor readings may therefore vary due to the ink characteristics rather than changes in the parameter that the sensor is intended to monitor. For example, different inks may have significantly different impedance characteristics, causing an impedance-based ink level detector or out-of-ink sensor to provide an inaccurate indication.
Second, variations between printers, and within one printer over time, may affect accuracy. Normal component tolerances in sensors and measurement circuitry and changes over lifetime can result in variations between printers, and changes in environmental variables, such as temperature, can cause measurement errors.
The problem of inaccurate or unreliable sensor readings is more acute in situations where the printer controller must distinguish between more than two discrete levels, such as when an inkjet printer controller must determine whether a portion of the ink delivery system contains ink, air, or xe2x80x9cfrothxe2x80x9d (a mixture of ink and air).
There is therefore a need for methods and apparatus that allow sensor threshold levels in printers to be adjusted for different ink or toner characteristics, and for variations between different sensors and printers.
Embodiments of the present invention include methods and apparatus for compensating for variations between different ink or toner characteristics, and for variations between sensors, by characterizing the ink or toner and storing one or more static threshold level on printer consumable memory devices during manufacture of the printer consumables. When installed in a printer, dynamic thresholds may be determined based on the static threshold level; the dynamic thresholds accounting for variations between sensors and printers. The dynamic thresholds may further be stored on the printer consumable memory devices.